1. Field of the Invention
The invention relates to a contact device which provides for self-adjusting contact with a removable contact finger of a distribution installation, the contact device being used for making electrical contact between the removable contact finger and either two by two, somewhat spaced-apart, electrically energized parallel running rails, or at least one grooved rail which is provided with parallel running, spaced-apart walls, the contact device intended for feeding electrical current between the rails and the removable contact finger.
2. The Prior Art
A contact device of the type herein contemplated is known, e.g. as discussed in a pamphlet of De Hoop/Groenpol Industrie Rotterdam B.V. With this known contact device the removable contact fingers extending from the back side of a removable block are provided with strip-shaped contact members which are bent in a U-shape configuration around these contact fingers, the contact members being both mechanically and electrically connected to the contact fingers by means of a bolt connection. The U-shaped contact member is shaped such that the closed side of the U-shape is not completely circular but is tapered somewhat to the centre such that the insertion of the contact device into the spacing between the rails is made easier. Further, the inner sides of the upstanding legs of the U-shape do not directly engage with the contact finger over their entire length but at both sides of the contact finger some space is left between this contact finger and the legs of the U-shape over a portion of the length of the upstanding legs. In addition, the distance measured over the outside of the upstanding legs of the U-shape is larger than the spacing between the rails into which the contact has to be pressed.
In this manner the required contact pressure is obtained by the elasticity of the U-shaped contact member. The advantage of such a contact device is that parts of the distribution installation can be altered or replaced in a simple and quick way without much work break-interruption.
An important disadvantage of the mentioned contact device, however, is that in case of a heavily increasing current, in particular a short circuit current, the contact pressure can be decreased such that an interruption with arc discharge occurs, during which the contacts may be welded together. When such welding occurs, the rails may be damaged such that a long breakdown may be caused due to the need for replacement of the damaged feeding rails. The reduction in the contact pressure is caused by the parallel flowing currents in the legs of the U-shaped contact member by which a force is generated which draws the legs towards each other. A further disadvantage of the known device is that although a good centering of the removable contact fingers with respect to the spacing between the rails is very important for establishing a good contact, in the case of a deviation from the necessary centered position of the contact fingers, the legs of the U-shaped contact member can be pressed sideways against the adjacent rails with different contact pressure on the two rails, resulting, in the most unfavorable case, in a loss of contact between one leg and one rail. Obviously this constitutes a contact of bad quality.
Accordingly it is an object of the present invention to provide a contact device in which the noted disadvantages are eliminated and in which the contact pressure is increased by the current flowing through the contact device, whilst the contact quality remains independent of the centered position of the contact finger between the rails.